format="HM" does work but displays as 0h 15m, I note in your previous post it works for you just displaying 15m, you any idea how I can get rid of the "0h" part?

Not until 3.2. I've got a to-do item to enhance HM to be HMS and recognize upper- versus lower-case. Upper means always display, lower means display only if non-zero. (And missing means don't display at all, so "HM" would mean always display hours and minutes, but never seconds, whereas "hmS" would mean always display seconds, and only display minutes if non-zero, and only display hours if non-zero).

format="HM" does work but displays as 0h 15m, I note in your previous post it works for you just displaying 15m, you any idea how I can get rid of the "0h" part?

Not until 3.2. I've got a to-do item to enhance HM to be HMS and recognize upper- versus lower-case. Upper means always display, lower means display only if non-zero. (And missing means don't display at all, so "HM" would mean always display hours and minutes, but never seconds, whereas "hmS" would mean always display seconds, and only display minutes if non-zero, and only display hours if non-zero).

any update on this matter Corey? I am currently using 3.2b2 with this:

<nobr> <duration break="+1" format="hm">, END L<roundbeforenextbreak>

which displays as

0h 15m, END L3

I would presume therefore that you didn't get the upper v lower case definition created in 3.2 or do I need to use it as an expression instead? even if I could have "mm" instead as an option that would sort that out and did you get the job done.

Also any progress on the variables to catch if there are no more breaks defined?